1. Field of the Invention
The present invention relates to an apparatus for cutting a sheet of paper in a small-sized printer for issuing vouchers or receipts, and more particularly to a paper cutting apparatus in a small-sized printer for consistently applying a compression force when a movable cutter is moved toward a fixed cutter to perform a cutting operation and accurately shifting from a rotative motion to a linear motion by a simple structure without dissipating motive power.
2. Description of the Prior Art
A small-sized printer of a variety of cash registers for issuing vouchers and receipts requires a paper cutting apparatus, and such a conventional paper cutting apparatus mounted to be used in various cash registers is illustrated in FIGS. 1, 2 and 3.
The conventional paper cutting apparatus, as shown in FIG. 1, includes a cutter base 1 placed at the lower side and a cutter cover 2 adapted to be coupled to cutter base 1 to cover the base. Referring to FIG. 2, cutter base 1 is formed with a narrow and horizontally-elongated paper inlet 12, and cutter cover 2 is formed with a paper outlet 21. Paper inlet 12 is provided with a fixed cutter 3.
A movable cutter 4 is disposed above cutter base 1 to reciprocate in a manner such that an edge of cutter crosses over cutter 3 to cut a sheet of paper passing through paper inlet 12.
Also, movable cutter 4 performs a linear reciprocating motion by means of a guide unit 8, and a motive power needed for the linear reciprocating motion is transmitted from a driving unit 90.
Guide unit 8 has a slide hole 13 in cutter base 1 elongated toward fixed cutter 3, and a slide plate 81 fitted into slide hole 13 while being fixed to the bottom plane of movable cutter 4. In addition, a plate 82 is fixed to the bottom plane of slide plate 81 to be wider than slide plate 81, and a pressing plate 19 pushes movable cutter 4 from the upper side thereof. Pressing plate 19, movable cutter 4, slide plate 81 and plate 82 are coupled as a unitary body by means of a pin member 91, and a shaft pin 92 is installed upright at the rear side for receiving the motive power.
Driving unit 90 includes a worm gear 95 fixedly installed to the bottom plane of cutter cover 2, a worm 96 for rotating worm gear 95 and a driving motor 54 fixedly installed with worm 96 connected to a motor shaft thereof. A swing lever 9 is furnished in such a manner to swing about one hinge point 98 of cutter base 1, lever 9 receiving a shaft pin 92 of movable cutter 4 in a slit 93 in the lever. The lever also receives a pin 97 on the worm gear 95 in a draw hole 94 in the lever.
In view of the above-described construction, worm 96 fixedly installed on the motor shaft of driving motor 54 rotates worm gear 95, and pin 97 on worm gear 95 is rotated one revolution to cause swing lever 9 to swing up and down once.
When swing lever 9 swings, shaft pin 92 inserted into slit 93 in the lever advances and retreats moving cutter 4. For this motion, cutter 4 performs a linear reciprocating motion under the guidance of guide unit 8 to cut the sheet of paper placed between movable cutter 4 and fixed cutter 3.
However, the foregoing conventional paper cutting apparatus has the problems listed below.
First, swing lever 9 is employed for converting the rotating motive power of the motor into the linear motion of movable cutter 4.
This involves the drawbacks of requiring lever 9, hinge point 98 for installing lever 9 and the necessary space to accommodate swinging lever 9 which requires a lot of parts and restricts the design.
Second, the motive power is greatly dissipated.
As mentioned above, movable cutter 4 receives the corresponding pressure where it is closely attached to cutter base 1 by means of pressing plate 19, and, as shown in FIGS. 1 to 3, both end portions of movable cutter 4 freely overlap the fixed cutter 3. Accordingly, movable cutter 4 can slant when it is moved in the advancing direction by an angle .theta..
If movable cutter 4 is moved forwardly in this state, angle .theta. is further increased this produces undesirable increase in the compression force and the load resistance.
That is, the state as shown in FIG. 2 is obtained in the initial state when movable cutter 4 starts to move in the advancing direction. Here, when movable cutter 4 is moved in the advancing direction, it is moved as shown in FIG. 3. At this time, if pressing plate 19 and movable cutter 4 are moved in the advancing direction, two points are fixed by shaft pin 92 and pin member 91 as shown in FIGS. 1 and 3. Due to this fact, the slant angle is further increased as movable cutter 4 is moved in the advancing direction.
The cutting load is gradually increased which incurs the problem of requiring a great force to perform the cutting operation.